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The reaction of an S- and O-bridged 8-quinolinolato trinuclear Mo cluster [Mo3OS3(qn)3(H2O)3]+ (3; Hqn = 8-quinolinol) with equimolar amts. of acetylenecarboxylic acid, 4-pentynoic acid, 5-hexynoic acid, HOAc, and pimelic acid gave clusters having μ-carboxylato groups, [Mo3OS3(qn)3(H2O)(μ-HC≡COO)] (6), [Mo3OS3(qn)3(H2O)(μ-H≡C(CH2)2COO)] (7), [Mo3OS3(qn)3(H2O)(μ-HC≡C(CH2)3COO)] (8), [Mo3OS3(qn)3(H2O)(μ-CH3COO)] (4), and [{Mo3OS3(qn)3(EtOH)}2(μ-C7H10O4)] (5), resp. X-ray structural analyses, 1H NMR, and electronic spectra of these clusters made clear that each of the COO- groups of the reagents bridges two Mo atoms in each cluster and that no adduct formation occurred at the sulfurs in the clusters. The reaction of 3 with a large molar excess (50 times) of acetylenecarboxylic acid gave [Mo3OS(μ3-SCH:C(COOH)S)(qn)3(H2O)(μ-HC≡CCOO)] (9) with two mols. of acetylenecarboxylic acid, one acting as a carboxylato bridge and the other in adduct formation, as supported by the electronic and 1H NMR spectra. The corresponding aqua cluster [Mo3OS3(H2O)9]4+ (1), on the contrary, reacts with acetylenecarboxylic acid to give [Mo3OS(μ3-SCH:C(COOH)S)(H2O)9]4+ (2).
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